PME Treasure

Why a script works in Blender's Text Editor but not from PME

3 min read

Symptom

A Python file succeeds when you press Run Script in Blender’s Text Editor, but the same file fails from a PME Command:

execute_script("scripts/my_tool.py")

The System Console reports an exception such as:

NameError: name 'Vector' is not defined

An old bug and today’s likely cause

The 2017 discussion exposed an old PME bug: an import visible to the file was missing inside one of its functions. The requester confirmed that moving the import into the function worked around it, and the bug was scheduled for a PME update.

PME 2.1 runs each file with one fresh set of global names, so a normal import at the top of the file is visible to functions defined during that run. There is no need to move every import into its function.

For a new NameError, check whether the file imports or defines the missing name. It may have been left behind by another Text block or console command during the successful test. execute_script() starts with PME’s standard names for that call, then adds kwargs and __file__; variables left in the Text Editor session are not copied into the run.

Fix

Make the file import every non-PME dependency it uses:

import bpy
from mathutils import Vector
 
 
def remap(value, old_min, old_max, new_min, new_max):
    point = Vector((0.0, 0.0, value))
    # Continue with the calculation...

Then invoke that same file again from PME, without first running another Text block that could hide a missing dependency.

If a top-level import succeeds but the imported name is still missing inside a function on PME 2.1, reduce the problem to a minimal file and report it. PME 2.1 should make the import visible to functions created in the same run.

Diagnostic sequence

  1. Open Blender’s System Console and read the first exception, not only the last line.
  2. For NameError, find where that name should be imported or defined.
  3. For ModuleNotFoundError, confirm that the dependency is available to Blender’s Python, not merely to a separate system Python.
  4. Reduce the file to its imports and one harmless statement, then add the real work back a section at a time.
  5. Re-test from the actual PME menu, editor, and mode as well as the Text Editor, because Blender’s operator context can differ.

What PME does provide

  • kwargs, containing values passed by the PME item;
  • __file__, containing the resolved script path;
  • core execution names such as C, D, bpy, and session-only U;
  • context-specific names when available—L while drawing UI and E while handling an input event.

O remains available as a compatibility shortcut, but bpy.ops is clearer in new long-lived scripts. return_value is not supplied in advance: assign it in the script when the caller needs a result. If the script does not assign it and execution succeeds, execute_script() returns True.

Those conveniences are not a substitute for ordinary Python imports. A reusable script should be understandable and runnable without relying on invisible session history.

Sources

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